The invention relates to wafer-level integration of focusing elements in semiconductor devices like optical sensors. Conventional focusing elements, usually lenses, are discrete elements arranged in the package of the device. They require a lot of space and increase the packaging costs.
US 2008/0237761 A1 discloses a system and a method for enhancing light sensitivity of a back-side illumination image sensor. An integrated circuit includes a substrate and an image sensor device comprising at least one transistor formed over a first surface of the substrate and a photosensitive region. A color filter is disposed over an opposite second surface of the substrate. A micro-lens structure is disposed between the second substrate surface and the color filter.
US 2005/0212132 A1 discloses a chip package including a rigid cover disposed above the active surface of the chip to protect the chip and to enhance the structural strength of the chip package. The rigid cover exposes a plurality of bond pads, which are arranged on the active surface of the chip and carry conductive bumps. The height of the bumps above the surface is larger than the height of the rigid cover.
US 2008/0011937 A1 discloses a solid-state imaging device comprising a distributed index lens formed of SiO2, a Si photodiode, wiring conductors and signal transmitting units.
US 2008/0261346 A1 discloses a semiconductor image device package comprising a microlens area formed on a die.
US 2013/0134535 A1 discloses a backside image sensor pixel. STI structures are used to form a backside focusing microlens as an integral part of a silicon substrate provided with photodiodes and transistors in a front surface.
US 2013/0168791 A1 discloses a back side illuminated CMOS image sensor comprising a substrate, a plurality of photo detectors and a plurality of microlenses on the bottom of a recess in the back surface. Additional circuitry on the chip may be included to amplify the voltage, and/or convert it to digital data.